Microencapsulation of drugs in biodegradable microparticles or microspheres is a well known pharmaceutical dosage preparation art. U.S. Pat. No. 6,599,627 cited herein for reference only; discloses one of the several ways known in prior art to prepare biodegradable microspheres for sustained drug delivery. The encapsulated drug particles can release a drug in a sustained manner ranging from few days and weeks to several months. However synthesizing microencapsulated drugs requires several chemical and physical steps, which leads to increased cost of preparation. The high surface area of such biodegradable microspheres also makes them more susceptible to bacterial contamination during preparation and uses. None of the known prior art references disclose methods of preparation of microspheres or microparticles or compositions of such microspheres or microparticles which are made in-situ and delivered during a surgical procedure and not in a factory setting.